Anaerobic membrane bioreactors for treating waste activated sludge: Short term membrane fouling characterization and control tests

There is limited information on the impact of sludge characteristics, membrane type and operation parameters on membrane fouling under anaerobic conditions. This paper examined filtration characteristics of anaerobic sludges with solids concentration between 6 and 33 g/L and the interaction with negatively and neutral charged membranes at various fluxes within the subcritical region. The study employed a short term filtration protocol using a bench-scale tubular ultra-filtration membrane operated at a cross-flow velocity of 1 m/s and under constant pressure. The results showed that the effects of anaerobic sludge concentration and membrane surface charge on membrane fouling were a function of the operating flux. Their impact on fouling was found to be minimal at the lower fluxes (8 LMH) however detrimental at higher fluxes (30 LMH). Further study on impact of anaerobic sludge composition on membrane fouling indicated that the decline in membrane performance at the higher subcritical fluxes was associated mainly with the colloidal fraction when the suspended solids concentrations were less than 20 g/L whereas at higher concentrations both the solids and colloidal fractions contributed to development of the fouling layer. Integration of a relaxation cycle and addition of cationic polymer were found to be effective in controlling anaerobic membrane fouling. (C) 2012 Published by Elsevier B.V.